Air mattress control unit

ABSTRACT

The system of the present invention is a system for supplying air and controlling the flow of air into and out of the chambers of a patient supporting air mattress. It includes an electric motor powered variable speed blower, a two position rotary valve, air mattress supply lines communicating between the rotary valve and the chambers of the air mattress, a continuous exhaust line also connected to the rotary valve, stepper motor controlled valves in the air mattress supply lines, pressure sensors between the stepper motor controlled valves and the chambers of the air mattress and a control unit for controlling the stepper motor controlled valves to control the amount by which the chambers of the air mattress are inflated.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional UtilityPatent Application Ser. No. 10/106,637 filed 26 Mar. 2002 now U.S. Pat.No. 6,698,046.

U.S. Non-Provisional Utility Application Ser. No. 10/106,637 claimed thebenefit of U.S. Provisional Patent Application No. 60/278,925 filed 26Mar. 2001 and U.S. Provisional Patent Application 60/292,090 filed 17May 2001.

FIELD OF THE INVENTION

This invention relates to a control system for controlling the flow ofair to and from the chambers of a low air loss, patient supporting airmattress.

BACKGROUND OF THE INVENTION

Numerous systems have been proposed for controlling the flow of air to alow air loss inflatable air mattress. For example, Suzuki et al., inU.S. Pat. No. 6,108,843 employed a set of on/off valves in combinationwith pressure sensors to control pressures within a set of air sacks ofan air mattress. Schild, in U.S. Pat. No. 5,117,518 discloses a rotatingvalve to alternately supply air to sets of air chambers in an airmattress. Thomas et, al, in U.S. Pat. No. 5,095,568 teach a flat platevalve system for distributing air to an air mattress.

The prior art evidences a search for a simple, reliable and compactmeans for providing a flow of air to the chambers of a low air loss airmattress. Numerous complex valves for controlling the flow of air havebeen developed.

One object of the present invention is to provide a simple, compact airmattress air supply and control system that is able to operate indifferent modes to supply air to different types of air mattresses.

Another object of the present invention is to provide an air mattressair supply and control system having a fan and motor that will not overheat as is now the case with many existing systems.

Yet another object of the present invention is to provide an airmattress air supply and control system that can receive an inputcorresponding to the weight of the supported patient, sense pressure inthe chambers of various zones of the mattress, convert those sensedpressures to interface pressures between the patient and the mattressdepending on the location of the zone and weight of the patent and thencontrol the flow of air to an air mattress so that the patient/mattressinterface pressure in each zone remains below a selected value toprevent the formation of bed sores.

Still yet another object of the present invention is to provide an airmattress air supply and control system that can be quickly deflated withreverse air flow so that cardiopulmonary resuscitation can beadministered to a patient supported by the mattress.

BRIEF DESCRIPTION OF THE INVENTION

The system of the present invention is a system for supplying air andcontrolling the flow of air into and out of the chambers of a patientsupporting air mattress. It includes an electric motor powered variablespeed blower, a two position rotary valve, air mattress supply linescommunicating between the rotary valve and the chambers of the airmattress, a continuous exhaust line also connected to the rotary valve,stepper motor controlled valves in the air mattress supply lines,pressure sensors between the stepper motor controlled valves and thechambers of the air mattress and a control unit.

The variable speed blower has an intake and an exhaust port. The inletport of the two position rotary valve is connected to the blower exhaustport. The two position rotary valve can either direct the flow of airfrom the blower to the chambers of the air mattress in a pressurizingmode or route the flow of air from the air mattress into the intake ofthe blower in a vacuum mode in which the air mattress is rapidlydeflated. When in the pressurizing mode, air exits the rotary valvethrough air mattress supply ports connected to the air mattress supplylines that supply air to various chambers of the air mattress. When inthe pressurizing mode, a portion of the air supplied by the blower alsoflows out of the rotary valve through the continuous exhaust line. Thecontinuous exhaust line provides a passageway for air to continuouslyflow through the blower to cool the blower. The stepper motor controlledvalves in the air mattress supply lines can incrementally close tocontrol the flow of air in the air mattress supply lines. The airpressure sensors which are located between the stepper motor controlledvalves and the chambers of the air mattress sense the air pressure inthe lines leading to the air mattress. The control unit receives signalsfrom the air pressure sensors and responds to those signals bycontrolling the operations of the blower and the stepper motorcontrolled valves in such a way that the air pressure within the airmattress chambers is held within a selected pressure range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the system of the present invention.

FIG. 2 is a perspective view of the rotary valve of the system of thepresent invention.

FIG. 3 is a bottom view of the rotary valve of the system of the presentinvention taken from plane 3—3 of FIG. 2.

DETAILED DESCRIPTION

The system of the present invention is shown on schematic FIG. 1. System10 includes an electric motor powered blower 15, an intake filter 30, 1two position-multiport rotary valve 100, air mattress supply lines 302A,302B, 302C, 302D and 302S for supplying air flow into and out of theinternal chamber(s) of an air mattress 400, continuous exhaust line 304,stepper motor controlled valves 310A, 310B, 310C, and 310D, pressuresensors 312A, 312B, 312C, and 312D, a control unit 50 and a controlpanel 70.

Variable speed blower 15 is powered by an electric motor (not shown)such as a 110V AC electric motor. Control unit 50 can control the powersupplied to the blower motor. Blower 15 is a single direction blowerthat is not a positive displacement air pump but rather a centrifugalfan type blower. This type of blower is appropriate in a system whichsupplies air to a low air loss air mattress such as air mattress 400.Air mattress 400 has a large number of small holes in its upper surfacesto permit air to constantly circulate around a supported patient.

Blower 15 has an intake port 17 and an exhaust port 19. Rotary value 100is shown schematically in FIG. 1 and is shown in greater detail in FIG.2. and FIG. 3. As is shown in FIG. 1, rotary valve 100 has an inlet port110 that is in pneumatic communication with exhaust port 19 of blower15. The blower intake port 17 is connected by an air tight chamber (notshown) to an outlet port 130 in rotary valve 100. As can be seenschematically in FIG. 1, rotary valve 100 includes a gate member 200,which in FIG. 1, is shown in a first position for directing air flow inan inflation direction while in a pressurizing mode. Rotary value 100has a set of mattress supply ports 112S, 112A, 112B, 112C and 112D aswell as a continuous exhaust port 114. Continuous exhaust port 114connects to a line 304 leading to the outside environment and provides apassageway for air to constantly flow through and cool blower 15. Supplyport 112S connects to a line 302S that might be used to inflate achamber or set of chambers of the air mattress that might remaininflated at a relatively constant pressure. A set of air mattress supplylines 302A, 302B, 302C and 302D connect to mattress supplyports 112A,112B, 112C and 112D respectively and are each interrupted by controlvalves 310A, 310B, 310C and 310D and pressure sensors 312A, 312B, 312Cand 312D respectively. Although, in the embodiment shown, air mattresssupply lines 302A, 302B, 302C and 302D each have a control valve and asensor, it is possible to configure a system where only some of thosesupply lines include a control valve and a sensor.

Each of these identical control valve, sensor arrangements can be betterunderstood by considering the control valve, sensor arrangement of airmattress supply line 302A which leads to a chamber or set of chambers inair mattress 400. Pressure sensor 312A, is used to sense the airpressure in line 302A. Control valve 310A controls the flow of air inline 302A between rotary valve 100 and air mattress 400. Control valve310A includes a stepper motor that incrementally opens and closes valve310A. Both pressure sensor 312A and control valve 310A are operativelyconnected to control unit 50 via lines 54A and 52A respectively.

Preferably, control unit 50 is a programmable control unit that canreceive inputs from a control panel 70. Control unit 50 is connected topressure sensors 312A, 312B, 312C and 312D via sensor lines 54A, 54B,54C and 54D respectively and to pressure control valves 310A, 310B, 310Cand 310D via control lines 52A, 52B, 52C and 54D respectively.Preferably, control unit 50 is also be operatively connected to themotor that powers blower 15 via a control line 53. Control unit 50receives signals from pressure sensors 312A, 312B, 312C and 312D andresponds to those signals by sending control signals to the steppermotors of control valves 310A, 310B, 310C and 310D and also, ifnecessary, by adjusting the amount of power supplied to the motor thatpowers blower 15.

The operation on one pressure sensor, control valve combination can beconsidered in order to understand the operation of all four pressuresensor, control valve arrangements. Control unit 50 receives a signalfrom pressure sensor 312A indicating the air pressure within the set ofchambers of air mattress 400 that are supplied by line 302A. Controlunit 50 responds to the pressure signal to determine if the pressure iswithin a selected range of pressures or above or below a selected rangeof pressures. Control unit 50 responds to the pressure signal by (1)transmitting a signal to incrementally close valve 310A when pressuresensor 312A indicates a pressure that is above the selected range ofpressures or by (2) transmitting a signal to incrementally open valve310A when pressure sensor 312A indicates a pressure that is below theselected range of pressures or by (3) transmitting a signal to the motorof blower 15 incrementally increase the supply of electrical power tothe blower motor to increase the blower output if pressure sensor 312Aindicates a pressure that is below the selected range of pressures andvalve 310A is completely open.

System 10 may be connected to a type of mattress having transverse airchambers arranged in zones much like the arrangement shown in FIG. 1 andcan be adapted to control the patient, mattress interface pressure toprevent the formation of bed sores. Control unit 50 could include analgorithm for converting sensed pressure to mattress, patient interfacepressure. The mattress, patient interface pressure is the pressure ofcontact between the mattress surface and the body of the patient. Ifthat pressure is too high, blood circulation under the patient's skin isrestricted and the patient develops bed sores. Such an algorithm wouldrequire an input relating to the weight of the patient and would convertthe measured back pressure from various zones of the mattress to anapproximate mattress, patient interface pressures. Control unit 50 wouldthen receive pressure values from pressure sensors 312A, 312B, 312C and312D and respond by either opening or closing valves 310A, 310B, 310Cand 310D to maintain pressure in the corresponding chambers of mattress400 to pressures that correspond to patient, mattress interfacepressures that are just below the acceptable value. In this way controlunit 50 can be adapted within the invention system to control pressurein a mattress to prevent bed sores.

The selected pressure range targeted by control unit 50 can be aconstant set of values or a set of values that change with timedepending on a pre-programmed mode that might be selected using controlpanel 70. Foe example, air mattress 400 might be configured differentlyfrom what is shown in FIG. 1, so that the set of chambers supplied byline 302A would all be on one lateral side of the air mattress. Controlpanel 70 might further have a mode selection option for a patientturning mode whereby chambers on alternate lateral sides of the airmattress are alternately inflated and deflated in unison in a cyclicfashion. In this case, the targeted pressure ranges would be constantlychanging as sets of air chambers are inflated and deflated.

System 10 may also be connected to another type of mattress havingtransverse air chambers arranged in a transverse, alternating manner. Apulsating air mattress could be arranged where such alternating,staggered sets of chambers would be inflated and deflated in accordancewith a programmed set of instructions.

Accordingly, system 10 is highly versatile and can be used to supply airto various types of air mattresses such as a rotational therapymattress, a pulsating mattress or constant pressure mattress.

System 10 is also capable of supporting a cardiopulmonary resuscitation(CPR) mode wherein an air mattress connected to the system can bequickly deflated so that the patient may be lowered to a firm surfacefor CPR. The CPR mode is activated by turning gate member 200 of rotaryvalve 100 to a second position shown in phantom in FIG. 1. When in thesecond position, gate member 200 directs air in a deflation directionfrom air mattress 400 into intake 17 of blower 15 while air leavingblower 15 is directed through filter 30 to the outside environment.Because air from air mattress 400 is now routed to intake 17 of blower15, air mattress 400 quickly deflates.

The arrangement of rotary valve 100 is illustrated in detain in FIG. 2.

As can be seen in FIG. 2, rotary valve 100 includes a valve housing 101and a gate member 200. Valve housing 101 has an open cylindrical shapeand includes an outer wall 105 and a base wall 102. Outer wall 105 hasan inlet port 110 that connects with exhaust port 19 of blower 15. Outerwall 105 of valve housing 101 also has air mattress supply ports 112S,112A, 112B, 112C and 112D for supplying air to various sets of chambersof air mattress 400 shown in FIG. 1 as well as a continuous exhaust port114. Air mattress supply ports 112S, 112A, 112B, 112C and 112D andexhaust port 114 are shown more clearly in FIG. 3 which is a view takenfrom plane 3—3 of FIG. 2. Base wall 102 of housing 101 has an outletport 130. Outlet port 130 and intake port 110 are centered upon the samediametric plane of housing 101.

Gate member 200 is received by valve housing 101 so that it can rotatewithin valve housing 101. Gate member 200 has a first circular end wall210 at one end, a second circular end wall 212 at the opposite end, acylindrical wall 216 and a horizontal wall 215 that extends between andconnects first end wall 210 and the second end wall 212. First end wall210 of gate member 200 comes into close proximity or contact with basewall 102 of housing 101 when gate member 200 in inserted into housing101. Second end wall 212 closes rotary valve 100 when gate member 200 ininserted into housing 101. Horizontal wall 215 divides gate member 200into a first portion which is above horizontal wall 215 in FIG. 2 and asecond portion which is below horizontal wall 215 in FIG. 2. Second endwall 212 has first ports 220 above horizontal wall 215. First ports 220could easily be combined into one port. First ports 220 can bepositioned anywhere in second end wall 212 above horizontal wall 215.First end wall 210 has a second port 230 positioned above horizontalwall 215 and a third port 232 positioned below horizontal wall 215. Ascan be better understood by referring to FIG. 1, ports 220 lead tofilter 30 and the outside environment. Cylindrical wall 216 of gatemember 200 is sized to fit within housing 101. An upper wall port 217opens into the upper chamber of gate member 200 while a very extensivelower wall port 218 opens up almost all of the lower chamber of gatemember 200. Although upper wall port 217 is shown in FIG. 2 as anopening in a substantially complete cylindrical wall 216, gate member200 can still function even if upper wall port 217 is as extensive aslower wall port 218. With such an open configuration, gate member 200presents first and second portions that are mostly bounded by the firstand second end walls of gate member 200, horizontal wall 215 andcylindrical outer wall 105 of housing 101 when gate member 200 isinserted into housing 101.

The various ports and openings of valve housing 101 and gate member 200are arranged so that the valve can operate in a first position in whichpressurized air is delivered to the air mattress a second position inwhich air is pulled from the air mattress to quickly deflate the airmattress. Air mattress supply ports 112S, 112A, 112B, 112C and 112D andexhaust port 114 are positioned in a pattern that is adjacent to inletport 110 so that when gate member 200 is tilted in the first position,air mattress supply ports 112S, 112A, 112B, 112C and 112D, exhaust port114 and inlet port 110 are on one side of horizontal wall 215 of gatemember 200 in communication with the second portion of the gate member.

When gate member 200 is in the first position, air can flow throughinlet port 110 of housing 101, into the second portion of gate member200 and then out through air mattress supply ports 112S, 112A, 112B,112C and 112D and exhaust port 114. Also while gate member 215 is in thefirst position, second port 230 of gate member 200 is aligned withoutlet port 130 of valve housing 101 (while third port 232 is blocked bybase wall 102 of valve housing 101) so that outside air can flow throughfirst ports 220 in second end wall 212, into the first portion of gatemember 200, through second port 230 of gate member 200, through outletport 130 of housing 101 and into the intake of blower 15. When gatemember 200 is in the first, pressurizing position, air from blower 15 isrouted to air mattress 400 shown in FIG. 1, while outside air is drawnin through filter 30 shown in FIG. 1 and into the intake of blower 15.

When gate member 200 is turned to a second position, horizontal wall 215is interposed between inlet port 110 and air mattress supply ports 112S,112A, 112B, 112C and 112D as well as exhaust port 114. When the gatemember 200 is in the second position, third port 232 of gate member 200aligns with outlet port 130 of housing 101 so that air is pulled inthrough air mattress supply ports 112S, 112A, 112B, 112C and 112D,through third port 232, then through outlet port 130 of housing 101 andinto the intake of blower 15. Also when gate member 200 is in thesecond, blower exhaust air passes through inlet port 110 of housing 101and out through first ports 220 into the outside environment (whilesecond port 230 is blocked by base wall 102 of housing 101). When gatemember 200 is in this second position, air is drawn out of air mattress400 shown in FIG. 1 and blower exhaust is expelled into the outsideenvironment through filter 30 shown in FIG. 1 causing air mattress 400to quickly deflate. To facilitate the vacuum mode, it may also beadvantageous to locate exhaust port 114 in an outside radial positionsuch as in the location of air mattress supply port 112B shown in FIG. 3and then to add a tab 240 to gate member 200 that only obstructs therelocated exhaust port 114 when gate member 200 is in the secondposition. This would stop air back flow through exhaust line 304 whenthe gate member is in the second, vacuum position. In the alternative,it may be advantageous to place a one way flapper valve in line exhaustline 304 to prevent such back flow when the system is operating in therapid deflating vacuum mode.

Preferably, rotary valve 100 can be fashioned from injected moldedplastic. It is preferable to mount gate member 200 in a spring biasedmanner so that gate member is pushed into housing 101 to make firmcontact. Because gate member 200 is intended to be operated manually, itmay also be advantageous to mount gate member 200 within housing 101 sothat it can only move between the first and second positions. Moreover,it would be preferable to have corresponding protrusions and recesses infirst end wall 210 of gate member 200 and base wall 101 of housing 101respectively that engage each other when gate member 200 is in a firstor a second position to provide an operator with tactile feed-back toindicate that rotary valve 100 is either in the first or the secondposition but not between the first or the second position.

It is to be understood that while certain forms of this invention havebeen illustrated and described, it is not limited thereto, except in sofar as such limitations are included in the following claims andallowable equivalents thereof

1. A system for supplying air and controlling the flow of air into andout of a plurality of chambers of a patient-supporting low air loss airmattress, the system comprising: a controllable blower having an intakeport and an exhaust port; air supply lines leading to the chambers ofthe air mattress; pressure sensors operatively connected to the airsupply lines; and a gate member, the gate member being operable from,and limited to, one of two positions by which the flow of air isselectively diverted, a first position in which air is permitted to flowsubstantially completely from the blower exhaust port to the chambers ofthe air mattress, and a second position in which the flow of air isrouted substantially completely from the air mattress into the blowerintake port, the system being configured to effect substantial and rapidevacuation of air from the air mattress when the gate member is in thesecond position, an amount of air flow being controllable from withinthe air supply lines.
 2. The system as recited in claim 1, wherein theair supply lines have electrically controlled valves for controlling theamount of air that can flow therethrough.
 3. The system as recited inclaim 2, wherein the air supply lines have the pressure sensorsinterposed between the valves and the chambers of the air mattress forsensing the air pressure in the chambers of the air mattress.
 4. Thesystem as recited in claim 2, further comprising a programmable controlunit connected to the blower, the pressure sensors, and the valves. 5.The system as recited in claim 4, wherein the control unit receivespressure signals from the pressure sensors and transmits a signal toincrementally close the valves in the air supply lines having an airpressure above the predetermined range of pressures.
 6. The system asrecited in claim 4, wherein the control unit receives pressure signalsfrom the pressure sensors and transmit a signal to incrementally openthe valves in the air supply lines having an air pressure below thepredetermined range of pressures.
 7. The system as recited in claim 6,wherein the control unit is able to transmit a signal to incrementallyincrease the supply of electrical power to the blower motor to increasethe blower output if pressure in an air supply line is below a selectedrange of pressures and the valve in that line is completely open.
 8. Thesystem as recited in claim 7, the control unit is able to receive inputsfor the height and weight of the patient, determine acceptable airmattress supply line back pressures corresponding to patient andmattress interface pressures given input values for patient weight andheight, whereby the values may be controlled to maintain patient andmattress interface pressures that are below pre-determined values. 9.The system as recited in claim 1, wherein the means for directing aircomprises a two-position rotary valve.
 10. The system as recited inclaim 9, wherein the rotary valve includes a housing defining an outletport, an inlet port, and air mattress supply ports.
 11. The system asrecited in claim 10, wherein the housing inlet port communicates withthe blower exhaust port, the air mattress supply ports communicate withthe air supply lines leading to the chambers of the mattress, and thehousing outlet port communicates with the blower intake port.
 12. Thesystem as recited in claim 9, wherein the gate member is rotatablyreceived by a housing of the rotary valve in the first or secondposition, the housing defining an outlet port, an inlet port, and airmattress supply ports.
 13. The system as recited in claim 12, whereinthe gate member has one or more ports able to align with the valvehousing inlet port when the gate member rotates in the first position,thereby allowing the gate member to communicate with the valve housinginlet port and air mattress supply ports, the blower intake tocommunicate with the outside environment, and the blower exhaust withthe air mattress supply ports.
 14. The system as recited in claim 12,wherein the gate member has one or more ports able to align with thevalve housing outlet port when the gate member rotates in the secondposition, thereby allowing the gate member to communicate with the valvehousing inlet port and the air mattress supply ports, the blower exhaustto communicate with the outside environment, and the blower intake withthe air mattress supply ports.
 15. A method for inflating and deflatinga patient support air mattress, the method comprising providing a blowerproducing air flow in pneumatic communication with an internal chamberof the air mattress, the blower including an inlet and an outlet;inflating the mattress by directing the flow of air substantiallycompletely to the mattress through a single inflation port of a valvehousing in an inflation direction from the blower outlet; and deflatingthe mattress in a substantial and rapid manner by directing the flow ofair substantially completely from the mattress through a singledeflation port of the valve housing in a deflation direction to theblower inlet, configuring the valve to operate from just two operativepositions for alignment with the single inflation port and the singledeflation port respectively for controlling the flow of air to and fromthe mattress.
 16. The method according to claim 15 wherein redirectingthe flow of air with the two-position valve comprises removing theblower outlet from pneumatic communication with the air mattressinternal chamber and placing the blower inlet in pneumatic communicationwith the air mattress internal chamber.
 17. The method according toclaim 16 wherein directing the flow of air in an inflation directioncomprises placing the blower outlet in pneumatic communication with theair mattress internal chamber, and directing the flow of air in adeflation direction comprises placing the blower inlet in pneumaticcommunication with the air mattress internal chamber for rapiddeflation.
 18. An inflatable patient support apparatus comprising: aninflatable mattress including an internal chamber, an air transmissiondevice operable to provide air flow into and out of the internalchamber, and a three port valve controlling the air flow to inflate ordeflate the mattress with the transmission device, the valve comprisinga rotary valve, the valve being operable from, and limited to, one oftwo positions by which the flow of air is selectively diverted, a firstposition in which air is permitted to flow substantially completely fromthe air transmission device to the internal chamber of the mattress, anda second position in which the flow of air is routed substantiallycompletely from the mattress into the air transmission device, the valvebeing configured to effect substantial and rapid evacuation of air fromthe mattress when the valve is in the second position, an amount of airflow being controllable from within the air supply lines.
 19. Theapparatus according to claim 18 wherein the air transmission devicecomprises a blower.
 20. The apparatus according to claim 19 wherein theblower comprises a single direction blower.
 21. The apparatus accordingto claim 18 further comprising a control unit, a plurality of sensors,and a plurality of pressure control valves, the mattress including aplurality of internal chambers, the pressure sensors providing pressureindication from the internal chambers to the control unit, and thecontrol unit opening or closing the valves to change pressure inside theinternal chambers.
 22. The apparatus according to claim 18 wherein themulti-port valve is manually operated.